1. Field of the Invention
This invention relates to detectors and, more particularly, to an array of photoconductive detectors.
2. Background Art
The use of photoconductive detectors for measuring radiation is well known. Because of their high sensitivity, photoconductive detectors such as PbS and PbSe are particularly effective in measuring infrared radiation. Detection of infrared radiation is used by the military for tracking warm vehicles and in night vision devices, is used by medical instrument manufacturers for measuring glucose and other body constituents in a noninvasive manner and is used by scientific instrument manufacturers for measuring chemical composition and structure.
In general, the resistance of the photoconductive detector changes when the radiation falls on its surface. Resistance changes can be measured as an electrical signal change and the intensity of the detected radiation can be estimated by the magnitude of resistance change.
Photoconductive detectors typically require a bias current or voltage to operate, such as a direct current bias. The sensitivity of the detector is proportional to the magnitude of the applied bias. It is preferred to supply a high bias to such a detector to increase its sensitivity and to overcome the noise of the electronics associated with the detector in an overall detection system.
It is common to use a plurality of photoconductive detector elements, also referred to as pixels, in the form of a linear array mounted on a common substrate to measure radiation across a spectrum of wavelengths. Each detector element is responsive to and detects a particular wavelength, or band of wavelengths, of radiation. In applications such as infrared scanners and cameras, it is a goal to integrate many photoconductive detector elements and their associated electronics into a single compact package.
It is an object of the present invention to provide a radiation detector which includes an array of photoconductive detector elements in which the performance of individual detector elements is alike. It is a further object to provide stability to the overall detector array both in terms of atmosphere and temperature stability, as well as in mechanical stability, and in an arrangement which is less complicated to manufacture than prior devices.